1. Field of the Invention
The present invention relates to an imprint apparatus and an article manufacturing method using the same.
2. Description of the Related Art
As the demand for microfabrication of semiconductor devices or MEMS increases, not only a conventional photolithography technology but also a microfabrication technology in which an uncured resin on a substrate is molded by a mold to thereby form a resin pattern on the substrate have been receiving attention. This technology is also referred to as an “imprint technology”, by which a fine structure with dimensions of a few nanometers can be formed on a substrate. One example of imprint technologies includes a photo-curing method. An imprint apparatus employing the photo-curing method first applies an ultraviolet curable resin (imprint material, photocurable resin) to a shot region (imprint region) on a substrate (wafer). Next, the resin (uncured resin) is molded by a mold. After the ultraviolet curable resin is irradiated with ultraviolet light for curing, the cured resin is released from the mold, whereby a resin pattern is formed on the substrate.
Since the internal atmosphere of the imprinting apparatus employing the aforementioned technology is basically gas (ambient air), air bubbles may be entrapped in a resin when a mold is pressed against the resin on a substrate. If the resin is cured with air bubbles entrapped therein, there is a high probability that defects will occur in the pattern to be formed. In order to avoid the occurrence of such pattern defects, Japanese Patent Laid-Open No. 2009-518207 discloses a method for removing gas between a mold and a resin in which the mold is temporarily deflected into a convex shape toward the substrate, a resin on the substrate is pressed against the mold in this state, and the mold is gradually restored to a flat surface so as to press the entire pattern surface against the resin. According to the method, gas present between the mold and the resin may be discharged from the inside to the outside, and thus, air bubbles entrapped in a resin may be reduced.
Furthermore, in the conventional imprint apparatus, if the mold is entirely released from the resin at one time, a large releasing stress is momentarily applied to the interface (contact portion) between the mold and the cured resin. Such a stress may cause distortion of the pattern to be formed in the resin, resulting in defects in the pattern. In contrast, in the apparatus disclosed in Japanese Patent Laid-Open No. 2009-518207, the mold is temporarily deflected into a convex shape when the mold is released from the resin in the same manner as when the mold is pressed against the resin. With this arrangement, the mold is gradually released from the periphery toward the center of the pattern-formed region of the cured resin. Consequently, the force required for a mold releasing is made smaller than that when no deflection is produced in the mold, and thus, the abrupt occurrence of stress can be avoided.
Here, as with the apparatus disclosed in Japanese Patent Laid-Open No. 2009-518207, if the mold is gradually deformed and released from the periphery toward the center of the pattern-formed region of the cured resin, the contact region between the mold and the resin gradually decreases and eventually disappears when the mold is completely released from the resin. However, the centroid of the contact region may be displaced from the center of the pattern-forming region in the course of the releasing operation depending on the deflection state of the mold or the layout of the pattern formed in the mold. Thus, if the position of the contact region is offset in the XY plane as described above, warpage of the mold increases at the portion where the distance between the boundary of the contact region and the end of the pattern-forming region to is close. The inclination of the concave and convex pattern (pattern section) formed in the mold increases with an increase of warpage of the mold. Consequently, the concave and convex pattern formed in the mold may be in contact with the pattern formed over the resin, resulting in the occurrence of defects such as pattern deformation, pattern damage, or the like.